DIY hovercraft guide - BR6

Let's start with the hovercraft hull. Cut a corrugated plastic plate 50 cm long by 25 cm large. The channels must be lengthwise.

Each time you cut a corrugated plastic piece, you can deburr the edges to get a smoother finish.

Draw four dots, each one being at 7,5 cm from both edges of the hull. Draw two lines to connect the dots as shown. These two lines measure 35 cm long and are separated by 10 cm. 

With a screw, drill three holes on each line, one at the center and the others at 2,5 cm from both ends of the line.

Cut two corrugated plastic strips 35 cm long by 2,5 cm large - again the channels must be lengthwise. Put them aside, we will use them later to set the skirt under the hovercraft. 

The side on which you draw the two lines is the underside of the hovercraft. Turn the hull over to work on the top.

In the center of the hull, at 1,5 cm from one of the edges, draw a 92 mm long by 65 mm large rectangle.

Cut three sides of the rectangle as shown on the picture. 

Using a non-sharp tool, strongly mark the last uncut side of this rectangle to break the corrugated plastic channels, then fold this piece.

You obtain the flap we talked about earlier : it will deflect part of the air towards the skirt.

Cut a 22 cm long by 8 cm large corrugated plastic plate, with the channels lengthwise. This is the motor support. 

At 6,4 cm from the edges of the motor support, draw two straight lines and strongly mark them with a non-sharp tool. Then fold this piece. 

Screw the motor support from below the hull, above the air deflector flap. Note that no screw should overlap on the two 35 cm lines you have drawn previously.

For all the steps of this build, please use your longest screws by default (from 3,5 cm to 4 cm) unless you are told otherwise.

Let a space of 1 cm between the rear of the hovercraft and the rear of the motor support (see next picture).

Solder two electric wires to the motor (around 50 cm each to be sure you have enough, you can cut the excess later).

I made a huge mistake purchasing single stranded electric wires, much less flexible, leading to terrible soldering. The HobbyKing link above will redirect you to the correct wires.

Put the propeller adaptor and the propeller on the motor axis. The Master Airscrew propeller I use here has a very thin shaft that I extended to 5 mm by carefully drilling it, but as this propeller is top of the line, it is worth the effort.

The propeller must be well wedged on its adaptor : if necessary, widen the propeller shaft, or on the contrary, add a shim to reduce its diameter.

To prevent injuries and damage, double check if the propeller is firmly attached on the motor shaft.

Cut two pieces of piano wire, 25 cm long. Make three turns with the piano wire around the two motor mounting screws.

In the end, the piano wire must be in a V-shape, forming a 50° angle (next picture shows it better). You should get a total length of around 8 cm of piano wire under the motor, and around 15 cm on the sides.

Fold the piano wire at 90° so that it is parallel to the motor axis. For the wires under the motor, fold at 2 cm from the screw. For the sides, fold at 3,5 cm from the screw. Work the wires until everything is folded correctly and as straight as possible - on the picture, this step is not finished yet.

This is a difficult step. Take your time and don't hesitate to start over if you get a bad result.

Finally, pay attention to the length of the two mounting screws : they should be long enough to hold the piano wire to the motor, but if you cannot turn the propeller manually without encountering any resistance, it means they're too long.

Pre-perforate the motor support in the four spots indicated with a straight rod of piano wire, then slowly insert the four "legs" of the motor into the motor support.

The entire length of the motor must be laid flat on the motor support, and the shaft must land right in the center. If you get a different result, the piano wire may be bent incorrectly, and you have to work them again to get a better result.

There should be a 5 mm gap between the hull and the propeller when it is oriented vertically. 

At the back of the motor support, on the sides, there should be a few extra centimeters of piano wire. Leave 1 cm and cut the rest. Bend the two rods inside the motor support like shown.

Drill two holes in the motor support at the rear of the motor to pass the thickest of your cables ties. Tighten it around the motor, then cut off the excess. Be careful not to tighten it too much, otherwise the motor support may deform in the long term.

The attachment of the cable tie should ideally be inside the motor support, and not outside as you can see here on the left : it will create a bit of drag.

If you have not done it yet, add electrical tape or heat shrink tubes to insulate the solders between the motor and the wires.

We continue with super-gluing the servo behind the motor. The servo arm should be aligned, or almost aligned, with the motor axis. Finer adjustment can be done later using the radio trim.

The servo arm will actually point the other way, towards the rear, as you will see on the next pictures.

Connect the servo extension cable and the servo to the appropriate channels on your receiver. As I have a 4-way radio set, my servo connects to "aileron channel", and my extension cable connects to "elevator channel". By default, check your radio manual to know what to do. Put the receiver into bubble wrap and tape it on the air deflector flap, while the antenna can be taped on the hull, next to the motor support. 

Pass the two electric wires inside the corrugated plastic plate, like shown on the picture, not too close to the motor support.

Close the back of the motor support with a small corrugated plastic plate (channels lengthwise for smoother finish). It is important to put the screws in the top of the plate, as shown on the picture, and not on the sides.

Also add two screws from the underside of the hull into this small plate. This will correct the deformation that usually appears at the rear of the hull after folding the air deflector flap.

There should be no need to access the receiver again during the assembly if you have made the correct connections for the servo and the ESC cable.

Cut two corrugated plastic pieces, 10 cm length by 7 cm height, with the channels heightwise. These are the steering flaps.

Take the lollipop stick and cut two pieces of 1 cm, they will be used to set the flaps to the correct height.

Cut two pieces of piano wire, respectively 38 cm and 14 cm length, and fold them in a U shape so the top rod measures 9,5 cm. The longest one will contain the two flaps spindles and the shortest one will be the flaps synchronisator. 

Work these U shapes until the rods are as straight as possible - again, at this point, I still had some work to do.

 Add duct tape on the front of the flaps to make them a bit more aerodynamic.

Using a rod of piano wire, pierce a hole on both sides in the last corrugated plastic channel of the motor support (one of the next pictures shows it a lot better).

Set the spindles into the 10th channels from the front of the flaps, add a piece of lollipop stick and push everything into the motor support. Then, set the flaps synchronisator in the last channel of both flaps.

To make sure the flaps synchronisator stays in place, pass a piece of synthetic thread through the last channel of one flap and knot it around the synchronisator at 2 cm from the flap.

Smear the knot with super glue to secure it, then cut the thread excess when the glue has dried. It isn't necessary to repeat this step on the other side.

Connect the flaps to the servo using two pieces of synthetic thread, each 25 cm long.

To get a good balance between angle of rotation and torque, I passed the threads in the 4th hole from the center of the servo arm, but other settings can be better - check this video to see a bit of theory about "control link geometry".

Drill two holes in each flap, just behind the spindles, at the height of the servo arm. Pass the threads through the holes and make two very tight knots. Smear them with a bit of super glue and let dry for a few hours, then cut the excess.

The flaps are finished. This is a side view of the left one.

You can see the spindle inserted in the last corrugated plastic channel of the motor support and the two holes where you pass the threads before knotting them.

Take the two corrugated plastic strips you cut earlier (35 cm long by 2.5 cm large) and screw them under the hovercraft through the six holes previously drilled, using 2,5 cm long screws.

The strips must be screwed exactly on the lines you have drawn at the beginning.

Cut a rectangle of wire mesh 38 cm long by 18 cm wide, then fold it to get the shape shown of the picture : 16 cm height at the back, a width of 5 cm, and 17 cm at the front : fold this extra centimeter as shown on the picture.

Make the necessary cutouts at the back of the wire mesh to allow the motor support and motor to pass through.

Round the top of the wire mesh by cutting a few meshes (from 9 cm height, cut 1 cm towards the center every 2 cm of height).

Pass the servo extension cable through a mesh, as far as possible from the propeller (you can see it on the left) and secure it with a bit of tape.

Complete the propeller protection with a corrugated plastic strip of 6,2 cm width and 48 cm length (channels lengthwise for better aesthetics). To give it the shape of the wire mesh, make a first fold at 11,5 cm from one edge, make another one 5,5 cm further, then 13 cm further and again 5,5 cm further. Screw this protection from below the hull with two screws on each side.

The center of gravity of the BR6 must be located not exactly in the middle of the hovercraft, but rather between 22 and 22,5 cm from the rear. You need to define where your battery should be located for the hovercraft to be correctly balanced.

When you have defined the place where your battery must be located, drill two holes to take out the electric wires previously inserted in the hull channels. Mines are at 15 cm from the front.

Congratulations for making it so far. As you can see, your BR6 is already looking great at this point.

Time to deal with the electronics. As you go along with this step, make sure to use electrical tape or heat shrink tubes to insulate the soldered connections.

Make a "box" that will contain the battery, the wires and the ESC and screw it from below the hull. A cover will then be screwed on top of this box to protect electronics from the water.

This box, and the battery it contains, should be positioned so that the center of gravity of the hovercraft is 22 - 22,5 cm from the rear. My NIMH battery will be positionned at 11 cm from the front, but you may get a different positioning with a lighter battery.

The result I obtained here isn't pretty nor clever - I will not be able to connect / disconnect the battery without unscrewing the cover first. You can get a better result by doing things differently and by adding a power switch.

Check out Mr Raynal's original pictures for another design.

You will now tape the skirt under the hull. It is imperative to take your time to do this correctly (up to an hour) to make sure everything is airproof and waterproof.

Remove the battery from its compartment and put the hovercraft upside down. If you respected the dimensions of the wire mesh and the corrugated plastic protection mentioned above, your BR6 can also stand on its right and left sides without being damaged. Do what feels most comfortable to you.

On the picture, you are facing the rear of the hovercraft, with the air deflector flap being in the upper right corner. At the center, you can see two of the four screws that hold the corrugated plastic protection around the wire mesh.

Tape the "outer rectangle" of the skirt to the hull, edge to edge. Start by taping two corners to tighten one side of the skirt, then add tape along the length. Do the same for the remaining sides, taping one corner at a time. This is certainly the most difficult step of the build : you will have to work in a smaller and smaller space as you tape the skirt.

It is also possible to tape the skirt on the upperside of the hovercraft - but as the tape will be visible on the upperside of the hull, the finish will be much worse.

Your BR6 is now finished. Congratulations on your work to build this RC hovercraft. Before operating your BR6 on water, I recommend that you give it a first try in a bathtub.

When not in use, keep your BR6 with a wedge under the motor support to avoid any deformation of the hull on the long-term.

The skirt is perfectly suited to smooth floors such as tiles or concrete slabs. Beware of rougher surfaces such as tar which can damage it. The skirt remains replaceable if necessary.